Wheels rotatably supported on fixed wheel brackets or yokes and casters are used in a wide range of industrial and commercial applications, and in many of these applications it is desirable to have a releasable braking apparatus incorporated into the wheel support structure to prevent rotational movement of the wheel. Further, in some applications wherein the wheel support structure is pivotal, it is desirable for the braking apparatus to be adapted to simultaneously prevent rotational movement of the wheel support structure relative to its pivot axis.
Wheels of the aforesaid type are typically supported for rotation by a bearing structure which is designed to withstand relatively large radial forces but is not adapted to withstand large axial forces. Thus, braking mechanisms which apply axially directed forces to one or both sides of a wheel can frequently produce axial force components on the bearing structure and rapidly decrease the operational life of the bearing. Accordingly, braking mechanisms which exert substantially radially directed forces on the wheel are considered superior.
A number of braking mechanisms for applying a radially directed force to a wheel have previously been developed, for example those disclosed in U.S. Pat. Nos. 1,733,536, 1,998,236, 2,096,229, 2,147,064, 2,695,683, 2,707,794 and 2,905,275. Although these braking mechanisms have generally been adequate for their intended purposes, they have not been satisfactory in all respects. In particular, each of these braking mechanisms applies a radially directed force to the tread provided on the periphery of the wheel. This can in some cases accelerate wear of the tread and thus reduce the life time of the wheel. More importantly, normal operational wear of the wheel tread and the presence thereon of foreign substances such as dirt or oil picked up during normal use can significantly degrade the operation of the braking mechanism.
In addition, the braking mechanisms disclosed in these patents are typically somewhat complex and require the assembly of several parts which can be manufactured only by several machining operations. Several of these braking mechanisms also have parts which project axially beyond the side flanges of the wheel supporting bracket or yoke and are thus subject to possible damage from impacts with objects the wheel support structure passes during normal operational use.
Moreover, of the braking mechanisms disclosed in these patents, only that disclosed in U.S. Pat. No. 2,707,794 is adapted to simultaneously prevent rotation of the caster wheel and pivotal movement of the caster yoke. This mechanism, however, as mentioned above, applies braking forces to the tread of the caster wheel. Further, this mechanism is relatively complex and is fully exposed, thereby increasing the likelihood of damage from impacts and reducing the aesthetic appeal of the caster.
Accordingly, it is an object of the present invention to provide a braking mechanism for a small wheel which is simple and inexpensive to manufacture and assemble, and which consists of a minimum number of parts which are preferably made by plastic injection molding techniques.
It is a further object of the present invention to provide a braking mechanism, as aforesaid, which is also adapted to releasably prevent pivotal movement of a caster yoke relative to the apparatus it supports.
It is a further object of the present invention to provide a braking mechanism, as aforesaid, which can be engaged and disengaged quickly and with minimal effort, but which effects secure braking of the wheel and/or caster yoke.
It is a further object of the invention to provide a braking mechanism, as aforesaid, in which braking forces are applied radially to the wheel, and are applied to a braking surface thereon other than the wheel tread.
It is a further object of the invention to provide a braking mechanism, as aforesaid, which is rugged and durable and requires little or no maintenance.
It is as further object of the invention to provide a braking mechanism, as aforesaid, in which braking of the wheel and caster yoke is actuated by a single manually operable lever.
It is as further object of the invention to provide a braking mechanism, as aforesaid, which is relatively compact and is disposed axially within the confines of the side flanges of the wheel supporting yoke.
It is a further object of the invention to provide a braking mechanism, as aforesaid, which is aesthetically pleasing and at least partially hidden from view.
It is a further object of the invention to provide a braking mechanism, as aforesaid, which can be retrofit into existing wheel and bracket units without modification of the bracket or wheel. In units where a bolt has been used to rotatably support the wheel on the bracket, the retrofit can be effected quickly and with the use of only simple hand tools.